Rep. Bill Cassidy (R-La.) will announce a run for a U.S. Senate seat on Wednesday, sources confirmed to POLITICO.

The impending announcement that he will challenge Democratic Sen. Mary Landrieu, first reported by The Associated Press, will take place in a video. Landrieu has been identified as a moderate Democrat that Republicans plan to target in 2014.

Cassidy, a doctor from Baton Rouge who was previously in the state Senate, will then launch an announcement tour in the state, a source also confirmed.

Joel DiGrado, who was Sen. David Vitter’s communication director during his 2010 campaign and was deputy state director for the Rick Santorum 2012 primary campaign, will be managing Cassidy’s campaign, a source with knowledge confirmed.

Vitter’s backing would likely give Cassidy a leg up in the race, particularly if the more tea party-aligned Rep. John Fleming or former Rep. Jeff Landry decided to run.

Many of Vitter’s staff moved over to work on Santorum’s 2012 campaign, which bested Romney by 22 percentage points in Louisiana. Vitter is rumored to be considering a 2015 run for governor, when Gov. Bobby Jindal’s (R) term expires. Having Vitter staff work on the 2014 Senate race would keep the senator’s voter identification records and ground operations fresh if he sought future elected office.

Vitter isn’t officially endorsing yet.

“My position in that race is and will remain that I will support the dominant Republican challenger to Mary as soon as that is clearly decided,” Vitter said in a statement.

The election system in Louisiana makes it less clear when a “dominant” challenger will be picked.

Louisiana does not use a primary system to elect officials. Instead, the state conducts open general elections where any number of candidates can run for office. If no candidate receives a simple majority, the top two vote-getters enter a runoff.

Even with the Cassidy announcement coming, Fleming isn’t ruling out a run.

“It’s imperative that Republicans have a strong conservative candidate to run against Mary Landrieu,” Fleming said in a statement. “I haven’t ruled anything out. The polling I’ve done has made it clear that a conservative Republican can defeat Mary Landrieu. So, whether it’s Bill or I, the critical issue is that Louisianians have a distinct choice.”

Louisiana Democrats pushed back on the Cassidy announcement.

“Bill Cassidy has spent his time in Congress fighting for extremists in Washington at the expense of the people of Louisiana. He is going to have a hard time convincing people in Louisiana that he has their best interests at heart when he repeatedly votes against hurricane protection and recovery funding and votes to give tax cuts to millionaires,” said Stephen Handwerk, executive director of the Louisiana Democratic Party.